The present invention refers to a coffee machine for brewing coffee powder pre-packed in a cartridge, comprising a perforator member for creating at least one opening in the cartridge.
In order to brew coffee powder pre-packed in a cartridge, up to now, mostly semi-automatic coffee machines are used in which the cartridge has to be inserted into a sieve holder with its cap facing downwards, whereby the sieve holder, thereafter, has to be manually fixed to the coffee machine. The coffee machine comprises a brewing pin member provided with radial outlet openings for the brewing water, located in the region of the portion pack holder fixing. The brewing pin member penetrates the bottom of the cartridge when the sieve holder is fixed to the coffee machine. The sieve holder itself is provided, at its bottom, with a plurality of projections. These projections penetrate the cap of the cartridge and perforate it, as soon as brewing water is fed to the sieve holder, whereby the cartridge is pressed against these projections under the influence of the hydraulic overpressure. At the consecutive brewing operation, the brewing water is fed into the cartridge by the brewing pin member, thus flowing through the coffee powder contained therein and escaping from the interior of the cartridge through the perforation in the cap. The freshly brewed coffee beverage can escape through outlets located at the lower side of the sieve holder. Such a coffee machine is disclosed, for example, in the document EP 0,891,734.
Practice has shown that the cross section of the brewing pin member that is relevant for the brewing water to escape the brewing pin member is relatively quickly decreased and fully blocked, respectively, under the influence of contamination. The reasons therefor are, for example, coffee fat, coffee particles as well as lime in the brewing water. However, with increasing contamination of the brewing pin member, the quality of the brewed coffee beverage decreases. From a hydraulic point of view, a further problem adhering to such brewing pin members is that so-called dead volumina occur in the interior of the cartridge such that portions of the coffee powder are not or insufficiently exposed to the flow of brewing water.
A further disadvantage of the mentioned brewing pin member consists in the fact that it leaves a relatively large puncture in the cartridge through which brewed coffee powder can escape once the brewing pin member is retracted, thus contaminating the coffee machine. This problem is particularly pronounced if the cartridge is put into the coffee machine such that the rear portion of the cartridge to be perforated extends vertically downwards, with the result that the brewed coffee powder can fall out of the cartridge under the influence of gravity, once the brewing pin member is retracted. Moreover, during the brewing operation and caused by the excess pressure in the interior of the cartridge, coffee powder escapes from the cartridge through a gap surrounding the brewing pin.
The document EP 0,521,187 discloses an apparatus for extracting closed cartridges. The apparatus is provided with an extraction head member, comprising a grid member for distributing the brewing water. The bottom side of that grid member is provided with protrusions adapted to perforate the cap of the cartridge to be extracted. The brewing water is supplied from the top through the cap of the cartridge. The latter one is bent under the influence of the pressure of the brewing water, with the result that an annular gap is created between the particular protrusion and the opening created therewith. Through that gap, the brewing water can get into the cartridge. The brewed coffee beverage is said to flow out downwards through the above mentioned outlet grid member. However, it is not quite clear how the brewed coffee beverage can escape the interior of the cartridge, because the protrusions extend through the therewith created openings, barely leaving any clearance between the particular protrusion and the opening created therewith.
Thus, it is an object of the invention to improve a coffee machine for brewing coffee powder pre-packed in a cartridge in such a way that it is of simpler design.
It is another object of the invention to improve a coffee machine for brewing coffee powder pre-packed in a cartridge in such a way that it is less susceptible to contamination.
It is a still further object of the invention to improve a coffee machine for brewing coffee powder pre-packed in a cartridge in such a way that it can be operated generally more reliably.
In order to meet these and other objects, the present invention provides a coffee machine for brewing coffee powder prepacked in a cartridge that comprises a perforator means for creating at least one opening in the cartridge containing the coffee powder. Thereby, the perforator means is adapted to create the opening in the cartridge bottom of the cartridge.
The perforator means has a cross sectional area that is smaller than the cross sectional area of the opening created in the cartridge bottom of the cartridge. Further provided are means for feeding brewing water under overpressure through the free cross sectional area of the opening in the cartridge bottom of the cartridge into the interior of the cartridge.